Low dropout (LDO) regulators are useful in applications where the regulator output voltage is not much lower than the input voltage, low power supply noise is required, and regulator power efficiency is not important. A low dropout voltage is achievable because the pass transistor in an LDO linear voltage regulator is a single transistor which can be driven very close to the triode region of operation. As a result, the dropout voltage, which is the minimum required voltage difference from the input to the output, is the lowest of any linear regulator type. Hence, low dropout regulators are useful in many circuits.